Mark Gertsvolf wrote:
> I am running Harmony JVM 5.0 on CentOS 5, x86 and I am using dnsjava
> library. The following simple A lookup works as expected with IBM JVM
> 5.0 and results in exception with Harmony.
>
> try {
> org.xbill.DNS.Record[] records = new
> org.xbill.DNS.Lookup("magma.ca").run();
> } catch (Throwable ex) {
> ex.printStackTrace();
> }
>
> Exception:
> java.nio.channels.IllegalSelectorException
> at
> java.nio.channels.spi.AbstractSelectableChannel.register(AbstractSelecta
> bleChannel.java:137)
> at
> java.nio.channels.SelectableChannel.register(SelectableChannel.java:115)
> at org.xbill.DNS.Client.<init>(Client.java:22)
> at org.xbill.DNS.UDPClient.<init>(UDPClient.java:14)
> at org.xbill.DNS.UDPClient.sendrecv(UDPClient.java:64)
> at org.xbill.DNS.SimpleResolver.send(SimpleResolver.java:256)
> at org.xbill.DNS.ResolveThread.run(ResolveThread.java:37)
>
> I studied dnsjava code and I do not see any reason for
> IllegalSelectorException to be thrown.
> http://dnsjava.cvs.sourceforge.net/viewvc/dnsjava/dnsjava/org/xbill/DNS/
> Client.java?revision=1.5&view=markup
> http://dnsjava.cvs.sourceforge.net/viewvc/dnsjava/dnsjava/org/xbill/DNS/
> UDPClient.java?revision=1.4&view=markup
>
>
> How does one troubleshoot this type of problem?
> Any help will be appreciated.
At the risk of sounding patronizing, "in a debugger" ;-)
In this case it would be possible to catch the IllegalSelectorException
and go in to look at how the program got there and the values of the
variables at the time.
I see that Client.java:23 is explicitly registering a selector with a
channel and giving an empty set of operations it is interested in, and
AbstractSelectableChannel.java:135 is throwing the exception if the set
is empty.
Here's a simple reproducer
public static void main(String[] args) throws IOException {
SocketChannel channel = SocketChannel.open();
channel.configureBlocking(false);
Selector selector = Selector.open();
channel.register(selector, 0);
}
I don't know why we forbid an empty set of interested operations?
If I remove the check my simple test above works...
Regards,
Tim
